Cyclopropanation of Cyclohexenone by Diazomethane Catalyzed by Palladium Diacetate: Evidence for the Formation of Palladium(0) Nanoparticles

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• 作者：Ona Illa ; Crist&oacute ; bal Rodrí ; guez-Garcí ; a ; Carles Acosta-Silva ; Isabelle Favier ; David Picurelli ; Antonio Oliva ; Montserrat G&oacute ; mez ; Vicen&ccedil ; Branchadell ; Rosa M. Ortu&ntilde
• 刊名：Organometallics
• 出版年：2007
• 出版时间：July 2, 2007
• 年：2007
• 卷：26
• 期：14
• 页码：3306 - 3314
• 全文大小：597K
• 年卷期：v.26,no.14(July 2, 2007)
• ISSN：1520-6041

文摘

The diazomethane-mediated cyclopropanation of cyclohexenone using Pd(OAc)₂ and different sourcesof Pd(0) species as precatalysts has been studied. In the presence of an excess of diazomethane, Pd(OAc)₂ rapidly evolves to the formation of palladium nanoparticles (less than 1 min), which are activeas catalysts in the cyclopropanation process. The nature of these particles has been analyzed throughtransmission electron microscopy showing a size distribution between 6 and 40 nm. These nanoparticlesgenerated in situ are more active than Pd(0) complexes, preformed nanoparticles, and commercial palladiumpowder. Cyclic voltammetry measurements of the reaction solution after completion show the presenceof Pd(0) species. This is the first time that Pd(0) nanoparticles are evidenced in a cyclopropanation reaction.Moreover, the reduction of Pd(OAc)₂ to Pd(0) in the presence of diazomethane has been theoreticallystudied through density functional calculations. The formation of methyl and allyl acetates as organicbyproducts has been predicted by the theoretical calculations, and these species, as well as oligomersderived from them, have been detected by spectrometric and spectroscopic techniques (MS, NMR,and IR).